Method and apparatuses for the production of synthetic air products and related gases

ABSTRACT

Processes and apparatuses are disclosed for the production of a synthetic air product with a variable oxygen content and a varying level of impurities.

TECHNICAL FIELD

[0001] The present invention relates to methods and apparatuses for the production of a synthetic air product utilizing distillation. The methods and apparatuses of the present invention capable of producing a synthetic air product of varying purity and content.

BACKGROUND ART

[0002] For purposes of this patent, the following terms are defined. As used herein, the term air separating unit or air separation unit means and refers to a facility, plant, location or process for separating the components of a feed gas and may include both cryogenic and non-cryogenic facilities. The term contaminant means and refers to impurities less volatile than oxygen. The term oxygen content means and refers to percent oxygen by volume. The term synthetic air means and refers to a product having an oxygen content of about 21% by volume. However, the term synthetic air product may be a processed product having any percent by volume oxygen content greater than about 15% by volume.

[0003] As used herein, the term feed air means and refers to atmospheric air. The term feed gas means and refers to a feed gas and may include feed air. The term oxygen supply means and refers to an oxygen supply with a determinable oxygen content and is not limited nor excluded from a pure supply, but rather, may be any concentration of oxygen. The term oxygen stream means and refers to a gas or gases with a determinable oxygen content. The term nitrogen supply means and refers to a supply with a determinable nitrogen content and is not limited nor excluded from a pure supply, but rather, may be any concentration of nitrogen. The term impurity and/or impurities means and refers to a component or components heavier than oxygen, i.e. a component or components with a higher boiling point than oxygen.

[0004] As well, the use of a particular structure, structures, or embodiments is not meant to be limiting. For instance, the term apparatus or apparatuses means and includes production facilities, plants, and the like. Further, the term process or processes means and includes methods, plans, production plans, and the like. The term led out means and refers to allowing out, passing out, discharging, releasing, and/or the like.

[0005] Various air separating units for accomplishing separation of feed gas do exist in the prior art and are well known. Generally, in air separating units, and more especially cryogenic air separating units, feed gas is first compressed by a compressor, and then passed through any manner of de-carbonating apparatuses known in the art, such as, and only by way of example and not as a limitation, an adsorber unit, a molecular sieve, and/or a decarbonating-drying portion; to remove carbon dioxide and moisture from the feed gas. Then the feed gas is cooled down by heat exchange in a heat exchanger, and rectified for separation in a rectification column so as to provide a product. Various examples of product gases include a nitrogen-enriched gas or liquid, a liquid rich in oxygen (also called sometimes liquid rich) at the bottom of the column, and other gases.

[0006] In some facilities the oxygen rich liquid bottoms is expanded to lower pressure and vaporized in the top condenser of the column to provide the cooling of this condenser. The vaporized rich liquid is called the waste stream. After this, nitrogen-enriched gas and/or waste stream are warmed to ambient temperature by heat exchanging with the feed gas in the main heat exchanger. Further, many other columns, rectification apparatuses, turbo expanders, valves, heat ex-changers, vents, phase separators and/or other like parts may be assembled in varying orders and assemblies to effect separation and/or production of gaseous components of a feed gas. Such other modifications of the assembly are well within the level of ordinary skill in the art.

[0007] Common examples of the separation of a feed gas into components are disclosed in U.S. Pat. Nos. 3,210,950 to Lady (the '950 patent), U.S. Pat. No. 5,901,577 to Pelle et al. (the '577 patent), U.S. Pat. No. 5,970,742 to Agrawal et al. (the '742 patent), U.S. Pat. No. 6,173,584 to Agrawal (the '584 patent), 5,836,174 to Billingham et al. (the '174 patent), 5,865,041 to Agrawal et al. (the '041 patent), U.S. Pat. No. 6,050,106 to Yamamoto et al. (the '106 patent), and others.

[0008] The '950 patent is representative of a method and apparatus for fractionating a gaseous mixture. The '950 patent discloses and teaches the separation of the gas by low temperature liquification and fractionation. Specifically, the patent is drawn to the advantages of a low temperature liquification and fractionation for the production of lower boiling point components in substantial purity. The patent teaches that the production of the lower boiling point components may be obtained by withdrawing the separation of the lower boiling point components and recycling this withdrawn material as a portion of the feed. However, the patent does not teach nor disclose the production of a synthetic air product of varying purity and content.

[0009] The '577 patent discloses a cryogenic process and plant for the production of gaseous oxygen. The patent discloses the use of a heat exchange line to cool the air by indirect heat exchange, an air distillation apparatus with a medium and low pressure column, and reboiler/condenser to which brings, into indirect heat exchange, vapor and liquid. Primarily, the vapor is a nitrogen product and the liquid is an oxygen product. However, the patent does not teach nor disclose the production of a synthetic air product of varying purity and content.

[0010] In fact, there have been several processes that have been directed toward the distillation of multi-component gaseous mixtures for the production of product streams. Examples of such processes are found in the '742 patent and the '584 patent. The '742 patent teaches a process for distillation of a multi-component stream, of three or more components, using a two-way communication path between two distillation columns at an end and a one-way distillation path from the other end between the two columns. However, the '742 patent does not teach nor disclose the production of a synthetic air product of varying purity and content. Likewise, the '584 patent teaches distillation of a multi-component streams, of at least three components, into at least four products from a first and a second distillation column. The '584 patent is different than the '742 patent because it uses a withdraw from an intermediate point along a column to produce a mixture stream that may be separated in a second distillation column. Therefore, two product streams may be produced from the top and bottom of both the first and the second distillation column and hence, four products. However, the patent does not teach nor disclose the production of a synthetic air product of varying purity and content.

[0011] The prior art also includes processes and apparatuses that have been developed for the production of an ultra high purity product from a distillation column(s). Examples of such processes and apparatuses are illustrated in the '106 patent. The '106 patent teaches and discloses the use of multiple rectification trays for the separation of a feed air. A stream is withdrawn at the top, the top defined as between a middle portion of the column and the absolute top, of the column containing an ultra high purity nitrogen product. A stream is withdrawn from the bottom of the column, defined as a point between the absolute bottom and the middle portion, containing an ultra high purity oxygen product. A stream may be withdrawn from the middle portion of the column to control the reflux of the column and refrigeration of the column. However, the patent does not disclose the production of a synthetic air product of varying purity and content.

[0012] Other patents in the art field teach and disclose the production of multiple product streams of varying concentration. One such example is the '174 patent. It teaches and discloses a cryogenic rectification system with two rectification sections in parallel for producing product oxygen at high and low impurities through a stripping process in the parallel columns. While he '174 patent may be effective in producing two product oxygen streams with low impuities, the patent does not teach nor disclose the production of a synthetic air product of varying purity and content.

[0013] As well, the '236 patent teaches and discloses a cryogenic rectification system for producing product oxygen at both high and low purity. Oxygen products of varying oxygen content are produced in this patent by the addition of a stripper column connected from a portion of the lower section of a main distillation column. The stripper column operates at a lower liquid to vapor ratio than the lower portion of the main column or uses more rectification trays to produce a higher purity oxygen product than that produced by the lower portion of the main distillation column. The higher purity oxygen product is removed from the stripper column. However, the patent does not teach nor disclose the production of a synthetic air product of varying purity and content.

[0014] The '041 patent teaches and discloses a process for cryogenic distillation of air to produce at least two oxygen rich streams of varying oxygen content. This patent withdraws at least two oxygen rich streams from a distillation column and injects the streams into a mixing column where at least two streams with different oxygen contents are removed. However, the patent does not teach nor disclose the production of a synthetic air product of varying purity and content.

[0015] The '174 patent, the '236 patent, and the '041 patent addressed an industry need for oxygen products with different levels of oxygen content. However, in various industries, instead of high purity nitrogen, oxygen or a combination, compressed dry air with a composition about that of atmospheric air, or about 21% oxygen content, is needed. One such industry is the medical gas industry, including the medical and medical supply industry, and semi-conductor industry. As well, some of these applications require products with varying oxygen contents that may be both above and below about 21%. However, it is common, but not always required, that the product is required to be free from moisture and carbon dioxide (CO2) and at least partially free from other contaminants. Most commonly, a level of contaminants tolerated for application of this type is in the ppb range (parts per billion). However, the level of contaminants tolerated can and often does vary depending upon a use of the product.

[0016] Industries that have such a need have referred to the product as a synthetic air or a synthetic air product. Because of this need, various attempts have been made in the prior art to simultaneously, with the production of nitrogen, oxygen, and/or other gases, to produce high purity synthetic air or a high purity synthetic air product. In one prior art attempt, a portion of the feed gas is passed through a decarbonating-drying adsorber. This portion of the feed gas is then taken out as a compressed dry air product. The production of a compressed dry synthetic air product by such method has proven effective, but does nothing- to very little for removing any contaminants from the feed gas, such as light hydrocarbons (methane, ethane etc.), and components with higher boiling points than oxygen, and the like. It is useful to note that the adsorbers utilizing molecular sieves can remove some heavy hydrocarbons (C4 and higher) but light hydrocarbons such as methane, ethane, propane can pass through such adsorber units. Therefore, the art field is in search of a method of removing contaminants from feed gas such that a higher purity synthetic air may be recovered.

[0017] U.S. Pat. No. 6,077,488 to Jain et al. teaches and discloses a process and apparatus for producing a clean dry air product using the absorbent beds mentioned above. A feed air is passed through an adsorption bed to remove moisture and carbon dioxide. Then the feed air is catalytically reacted to convert the impurities to moisture and carbon dioxide. Further, the feed is passed again over an adsorption bed to remove the moisture and carbon dioxide produced from the catalytic conversion. However, the patent does not disclose the production of a synthetic air product of varying purity and content.

[0018] Another prior art solution to overcome this problem is an air separating unit which can simultaneously generate high purity nitrogen gas and compressed dry synthetic air of high quality freed of light hydrocarbons such as methane and ethane. Hydrocarbons and components heavier than nitrogen and oxygen, whose boiling points are higher than that of nitrogen or oxygen, are partially removed from the feed gas in a lower rectifying portion of a rectification column as is shown and described in U.S. Pat. No. 5,546,765 to Nagamura et al. (the '765 patent). This patent discloses a rectification portion of a column whereby hydrocarbons, krypton and xenon are removed from feed gas before synthetic air is removed.

[0019] The air separating unit of the '765 patent uses feed gas taken from the atmosphere, cooled down near to its liquefying point by a heat exchanger, after it is compressed and freed of hydrogen, carbon monoxide, carbon dioxide, and moisture. Then, the cooled feed gas is introduced into a rectification column. Nitrogen gas is separated by rectification from the feed gas in the rectification column and is liquefied by condensation in a condenser. The liquid nitrogen liquefied by condensation in the condenser is introduced into the top portion of the rectification column as a reflux liquid, and a part of the reflux liquid is led out of the rectification column, thereby producing a liquid nitrogen product. Further, nitrogen products may be extracted at the top of the column. The rectification column is further characterized in that the rectifying portion of the rectification column is divided into a lower rectifying portion and an upper rectifying portion. The lower rectifying portion is made to have such a minimum dimension of height as required for removing hydrocarbons such as methane and ethane from the feed gas so that the total content of such hydrocarbons is lowered from the initial content. The gas or gases, essentially freed, of hydrocarbons is then taken out as a compressed dry air product from a space between the lower rectifying portion and the upper rectifying portion.

[0020] However, a synthetic air product produced by this process yields a synthetic air product with an oxygen content of about 5% to about 15% by volume because the use of rectifying trays in the column reduces the oxygen content of the product gas extracted above the feed tray. Accordingly, the art field is in search of a process or processes and an apparatus or apparatuses for producing a synthetic air product with a variable oxygen content that has a capability of producing a synthetic air product with an oxygen content above about 15% and varying level of impurities.

[0021] However, there have been various attempts in the art field to make such a product. Such attempts in the art field include the making or production of a synthetic air product from liquid nitrogen and liquid oxygen. In processes of this type, the oxygen and nitrogen have been directly mixed. However, the liquid supplies often contain impurities at a level that is not acceptable for a high purity synthetic air product. One such process is disclosed in U.S. Pat. No. 4,181,126 to Hendry (the '126 patent). This patent discloses a cryogenic underwater breathing apparatus where liquid nitrogen and liquid oxygen are mixed to obtain a synthetic air product that will have the impurity levels of the mixed liquid supplies. Accordingly, the art field is in search of a process and apparatus for mixing a liquid nitrogen and liquid oxygen supply that will remove impurities during the production of the synthetic air product.

[0022] A prior art process that is used for the production of various gases for semiconductor production facilities is disclosed in U.S. Pat. No. 5,656,557 to Hata et al. (the '557 patent). The '557 patent discloses a process that allows for the production of a high purity nitrogen product and a synthetic air product. The patent discloses passing a feed air stream over an adsorber to remove moisture and carbon dioxide and then catalytically removing the hydrocarbons and hydrogen. A portion of the feed air is then removed as a synthetic air product while the remainder of the feed air is introduced to a column for the production of a nitrogen product. However, the patent does not teach nor disclose the production of a synthetic air product of varying purity and content.

[0023] Further U.S. Pat. No. 4,848,996 (the '996 patent) discloses a modifications to the basic nitrogen generation process. This patent discloses distillation trays that are added in a fractionation section above the top condenser of the column for the purpose of stripping oxygen from the gaseous-oxygen enriched stream. The gaseous stream removed from this fractionation section is described to be of a composition similar to air, and the “synthetic air is recycled for compression and mixing with main air feed stream to the bottom of the distillation column. The purpose of the recycling of “synthetic air” is to improve the efficiency of the nitrogen production cycle. However, the patent does not teach nor disclose the production of a synthetic air product of varying purity and content.

[0024] A further modification of the '996 patent is disclosed in U.S. Pat. No. 4,927,441 (the '441 patent). The '441 patent discloses another modified version of the '996 to further improves the efficiency of the nitrogen production. However, the patent does not teach nor disclose the production of a synthetic air product of varying purity and content.

[0025] Some prior art patents have modified the above techniques by recycling a “synthetic air” in another column. U.S. Pat. No. 5,711,167 discloses such a technique where the vapor portion of the partially vaporized rich liquid of the bottom of the column is recycled back to the column to improve the distillation for nitrogen production. However, the patent does not teach nor disclose the production of a synthetic air product of varying purity and content.

[0026] An attempt to improve nitrogen production is disclosed in U.S. Pat. No. 4,966,002 (the '002 patent). The '002 patent discloses a process where a portion of vaporized rich liquid is recycled and the remaining portion is expanded to improve the performance of the nitrogen production. However, the patent does not teach nor disclose the production of a synthetic air product of varying purity and content.

[0027] Other patents have used processes and principals similar to the ones described above, such as U.S. Pat. Nos. 4,867,773, 4,883,519, and 5,385,024. These patents are for the improvement in the efficiency of the production of nitrogen by cryogenic distillation. However, these patents do not teach nor disclose the production of a synthetic air product of varying purity and content.

[0028] None of the prior art herein described has taught or disclosed the production of a synthetic air product that is selectively free of impurities. Moreover, none of the prior art herein described has taught or described the production of a synthetic air product capable of processes where the oxygen content of the synthetic air product may vary. Accordingly, the art field is in search of processes and apparatuses to enable the production of a synthetic air of varying removed and a varying oxygen content.

SUMMARY OF THE INVENTION

[0029] The present invention generally relates to processes and apparatuses for the production of a synthetic air product. The synthetic air product may be selectively produced with a varying oxygen content and/or varying levels of impurities.

[0030] This summary is not intended to be a limitation with respect to the features of the invention as claimed and any examples are merely intended as embodiments, and the scope and other objects can be more readily observed and understood in the detailed description of the preferred embodiment and the claims.

BRIEF DESCRIPTION OF DRAWINGS

[0031] For a further understanding of the nature and objects of the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein:

[0032]FIG. 1 is an illustration of an embodiment of an apparatus of the present invention.

[0033]FIG. 2 is an illustration of an alternate embodiment of an apparatus of the present invention.

[0034]FIG. 3 is an illustration of an alternate embodiment of an apparatus of the present invention.

[0035]FIG. 4 is an illustration of an alternate embodiment of an apparatus of the present invention.

[0036]FIG. 5 is an illustration of an alternate embodiment of an apparatus of the present invention.

GENERAL DESCRIPTION AND PREFERRED MODE FOR CARRYING OUT THE INVENTION

[0037] For purposes of the description of this invention, the terms “upper”, “lower”, “right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, and other related terms shall be defined as to relation of embodiments of the present invention as it is shown an illustrated in the accompanying Figures. Further, for purposes of the description of this invention, the terms “upper portion,” “lower portion,” “top,” “bottom,” and the like shall be defined to mean an upper portion and a lower portion and not specific sections. However, it is to be understood that the invention may assume various alternative structures and processes and still be within the scope and meaning of this disclosure. Further, it is to be understood that any specific dimensions and/or physical characteristics related to the embodiments disclosed herein are capable of modification and alteration while still remaining within the scope of the present invention and are, therefore, not intended to be limiting.

[0038] Referring now to FIG. 1, an illustration of an embodiment of an apparatus of the present invention for production of a synthetic air product, a flow diagram showing an embodiment of an air separation column. Generally, a compressed feed gas is supplied to the system through feed gas supply line 1. The feed gas may be compressed by any method common in the art, such as compressor 15 and the like.

[0039] Feed gas supply line 1, in an embodiment, is then passed through a CO2 and Moisture Removal Unit 16. CO2 and moisture removal unit 16 is a de-carbonating and drying unit that removes carbon dioxide and moisture in the feed gas. CO2 and moisture removal unit 16 may be of any method and/or apparatus common in the art. In an embodiment, unit 16 is an alumina combined molecular sieve portion. Other embodiments use a molecular sieve. Further embodiments include a CO2 and moisture removal system that uses a heat exchanger to freeze the CO2 and moisture and separate it from the feed gas.

[0040] In an embodiment, feed gas supply line 1 then passes through a heat exchanger 2 where the feed gas is cooled by indirect heat exchange with a synthetic air product in line 13 and a waste product in line 11. However, various other embodiments of the present invention may use different streams to effect cooling of the feed gas and/or different processes and apparatuses to cool the feed gas. In an embodiment, the feed gas is cooled within feed gas supply line 1 to about its dew point or about its liquefying point before cryogenic distillation. However other embodiments of the invention may cool the feed gas to its liquefying point within the distillation column or may cool the feed gas to a different temperature level.

[0041] While an indirect heat exchanger has been illustrated for an embodiment of the invention, other embodiments may use any method for cooling common in the art. For example, and not by way of limitation, various embodiments incorporate a turbo expander (not shown) or a liquid stream (liquid assist) that is vaporized in the process to supply the cold for the process. An embodiment utilizing a turbo expander may use a portion of a vaporized liquid bottoms removed from column 5. However, various other embodiments may utilize other sources for the cooling common in the art.

[0042] Referring back to FIG. 1, the oxygen content of the feed gas is enhanced by oxygen enhancing line 22. The oxygen content of the feed gas may be enhanced by an oxygen supply added to the feed gas. Depending upon the location of the injection, mixing point, or contact point, the oxygen supply may be in any form, such as a liquid, gas, a mixture of the aforementioned, and/or the like. In an embodiment, the oxygen content is increased to between about 21% by volume to about 40% by volume. However, the oxygen content may be increased to any desired level.

[0043] In an embodiment, the oxygen is added prior to drying and de-carbonating of the feed gas. Other manners of addition of the oxygen supply will be readily apparent to those of skill in the art and are fully covered by this disclosure. In various embodiments varying levels of impurities, such as, for example and not by way of limitation, moisture, carbon dioxide, hydrogen, and hydrocarbons, may be removed. The feed gas is then passed into a distillation column 5. In FIG. 1 the feed gas is passed to a lower portion of a cryogenic distillation column 5.

[0044] In column 5, there is provided at least one tray 6 for rectification. Column 5 is equipped with at least one tray or contacting device, such as structure packing or other rectification trays for removing impurities from the feed gas. In another embodiment, there are multiple trays 6 for removing impurities. As feed gas is supplied to column 5 the feed gas will begin to separate and rectification will occur across the at least one tray 6.

[0045] A line 8 from a lower portion of Column 5 provides a path for oxygen-enriched liquid bottoms, or liquid bottoms, to flow. A portion of the oxygen-enriched liquid bottoms is then vaporized and passed out waste line 11. The vaporized bottoms serves to condense rising gas in column 5 as will be more fully described herein below. Other embodiments may collect a portion of the oxygen enriched liquid as a product or for other distillation or rectification purposes. Such other purposes are well known in the art field and are fully included in this disclosure.

[0046] The portion of the oxygen enriched liquid extracted at the bottom of column 5, in an embodiment, is expanded to a lower pressure and sent to the condenser where it is vaporized against condensing gas of the top of the column. Liquefied condensing gas is returned to the column as liquid reflux stream. Various embodiments utilize waste line 11 as a coolant for indirect heat exchange in heat exchanger 2. Other embodiments may use waste line 11 in another process or for another purpose, as will be readily apparent to those of ordinary skill in the art.

[0047] In an embodiment, the portion of feed gas rising in column 5 is brought into gas-liquid contact in a countercurrent state with a reflux liquid flowing down from above. As a result, the downward liquid flow is gradually enriched in components whose boiling points are higher than that of nitrogen to become oxygen-enriched liquid. In the same manner, upward rising vapor is gradually enriched in nitrogen to become nitrogen-enriched gas.

[0048] Nitrogen enriched gas which has passed through column 5 may be extracted as synthetic air product through about line 13. The oxygen content of the synthetic air product removed about line 13 will vary dependant upon many factors, including, but not limited to, the number of rectification trays and the amount of oxygen supply added to the feed gas.

[0049] The synthetic air product withdrawn at about line 13 may have any desired oxygen content. In one embodiment, the oxygen content is about 21% by volume. In another embodiment, the oxygen content is about 15% by volume to about 40% by volume. In another embodiment, the oxygen content is about 20% by volume to about 30% by volume. However, an oxygen content of varying percentage may be withdrawn dependant upon several factors, including, but not limited to, the number of tray(s) 6 and the oxygen enhancement of the feed gas. In embodiments utilizing a heat exchanger, the synthetic air product may be warmed in indirect heat exchange with feed gas to allow the temperature of the product to approach ambient.

[0050] Synthetic air products produced by this process and apparatus may be used as medical gases or for other end user requirements. While a compressed synthetic air product gas has been disclosed, the synthetic air product can be liquefied to yield a liquid synthetic air product.

[0051] Now referring to FIG. 2, an illustration of an alternate embodiment of an apparatus of the present invention for production of a synthetic air product, a different location for oxygen content enhancement is illustrated. In this embodiment, oxygen enhancing line 23 is connected to feed gas supply line 10 after heat exchanger 2.

[0052] Now referring to FIG. 3, an illustration of an alternate embodiment of an apparatus of the present invention for production of a synthetic air product, a different location for the oxygen content enhancement is illustrated. In this embodiment, oxygen enhancing line 25 is connected directly to column 5. Here, in an embodiment, oxygen enhancement occurs with the feed gas at a portion of column 5. In an embodiment, oxygen is added to the distillation column below at least one tray 6.

[0053] Now referring to FIG. 4, an illustration of an alternate embodiment of an apparatus of the present invention for production of a synthetic air product, a different location for the oxygen content enhancement is illustrated. In this embodiment, oxygen enhancing line 26 is connected directly to column 5 at a tray located at least one theoretical tray or real tray above the connection of feed gas supply line 10 to column 5. Here, oxygen enhancement of the feed gas occurs after the feed gas has been introduced to column 5. In various embodiments, oxygen enhancing line 26 is connected to column 5 above at least one real or theoretical tray. In other embodiments, oxygen enhancing line 26 may be connected to column 5 above more than one tray. As in the prior figures, oxygen supplied to the feed gas through oxygen enhancing line 26 may be cooled prior to introduction, but such cooling is not required. Other embodiments may also remove various impurities to the oxygen before introduction to the feed gas, such as, for example and not by way of limitation, moisture, carbon dioxide, hydrogen, and hydrocarbons.

[0054] Now referring to FIG. 5, an illustration of an alternate embodiment of an apparatus of the present invention, a compressor is not used. An oxygen supply 27 and an other supply 28 are supplied for mixing. In an embodiment, at least one of the oxygen supply and the other supply are a liquid. In such cases, the liquid is, vaporized in a vaporizer 30 and/or 31 and mixed in feed gas supply line 1 for the production of a mixture before rectification. In an embodiment, the other supply 28 is a nitrogen supply. As well, other embodiments may use other methods of vaporizing liquid and mixing of the components, such as mixing prior to introduction to feed gas supply line 1. As in the other embodiments herein disclosed, varying number of at least one tray(s) 6 may be used in column 5 depending upon the level and type of impurities sought to be removed.

[0055] The present invention further discloses a process or method for preparation of a synthetic air product. The process generally includes the cryogenic rectification of a feed gas that has been enhanced by an oxygen stream. The process yields a synthetic air product with varying percentage of oxygen content. Other embodiments of the present process may include additional columns, trays and removals of other products, such as an oxygen enriched product, a nitrogen enriched product, and others. Other embodiments may incorporate the use of a CO2 and moisture removal unit. Other embodiments may utilize the mixing of a vaporized liquid nitrogen and a vaporized liquid oxygen before rectification, including the mixing of a gaseous source. Other embodiments may utilize a mixing of an oxygen supply and a nitrogen supply during rectification. Varying other embodiments of the present process will be readily apparent to those of ordinary skill in the art.

[0056] Although various embodiments of the present invention have been shown and described, various other modifications may be made to the present invention while keeping within the scope and content of the claims of the present invention. For instance, the present invention is not intended to be limited to an embodiment for the production of a synthetic air or a synthetic air product, but rather may be a portion of a larger air separation process or other process. 

What is claimed is:
 1. A process for the production of a synthetic air product comprising the steps of: supplying a feed gas; enhancing the oxygen content of the feed gas; passing the feed gas to a cryogenic distillation column; rectifying the feed gas in the distillation column to remove impurities; and, extracting a synthetic air product at least a real or theoretical tray above where the feed gas is passed to the column.
 2. The process of claim 1 further comprising compressing the feed gas.
 3. The process of claim 1 wherein the step of enhancing the oxygen content of the feed gas comprises mixing an oxygen stream with the feed gas.
 4. The process of claim 2 wherein the oxygen content of the feed gas is enhanced prior to fully compressing the feed gas.
 5. The process of claim 1 wherein the oxygen content of the feed gas is enhanced prior to fully rectifying the feed gas.
 6. The process of claim 1 wherein the oxygen content of the feed gas is enhanced prior to fully cooling the feed gas.
 7. The process of claim 1 wherein the oxygen content of the feed gas is enhanced at a point in the distillation column.
 8. The process of claim 7 wherein the synthetic air product is extracted at least one real or theoretical tray above the point in the distillation column.
 9. The process of claim 1 wherein the feed gas is cooled to generally about a dew point of the feed gas.
 10. The process of claim 1 the feed gas is air.
 11. The process of claim 1 wherein the step of enhancing the oxygen content further comprises mixing an oxygen supply with the feed gas.
 12. The process of claim 11 wherein the oxygen supply is greater than 90% by volume.
 13. The process of claim 1 wherein the step of rectifying the feed gas further comprises more than one tray.
 14. The process of claim 1 further comprising the step of removing a nitrogen enriched product.
 15. The process of claim 14 wherein the nitrogen enriched product is removed along an upper portion of the column.
 16. The process of claim 1 wherein the synthetic air product extracted has an oxygen content of about 15% by volume to about 40% by volume.
 17. The process of claim 1 wherein the synthetic air product extracted has an oxygen content of about 20% by volume to about 30% by volume.
 18. The process of claim 1 wherein the synthetic air product extracted has an oxygen content of about 21% by volume.
 19. The process of claim 1 wherein the step of supplying the feed gas further comprises mixing an oxygen supply with an other supply prior to rectifying.
 20. The process of claim 19 wherein at least one of the oxygen supply and the other supply is a liquid.
 21. The process of claim 19 wherein the other supply is a nitrogen supply.
 22. A cryogenic process for the production of a synthetic air product including the steps of supplying a feed gas; substantially removing CO2 and moisture from the feed gas; mixing the feed gas with an oxygen content enhancing stream; cooling the feed gas, passing the feed gas into a distillation column; and, removing a synthetic air product.
 23. The process of claim 22 further comprising compressing the feed gas.
 24. The process of claim 22 wherein the step of supplying the feed gas further comprises mixing an oxygen supply and an other supply.
 25. The process of claim 24 wherein at least one of the oxygen supply and the other supply is a liquid.
 26. The process of claim 25 wherein at least one of oxygen supply and the other supply is a gas.
 27. The process of claim 24 wherein the other supply is a nitrogen supply.
 28. An apparatus for producing a synthetic air product comprising: a column having an upper portion, a lower portion, a top, a bottom, and at least one tray; a feed gas supply line connected to the column; an oxygen content enhancing line connected to the feed gas supply line; and, a product withdraw line connected to a portion of the column for removing a synthetic air product.
 29. The apparatus of claim 29 further comprising a line connected to the lower portion of the column to remove rich liquid.
 30. The apparatus of claim 29 wherein the oxygen content enhancing line is connected to the column.
 31. The apparatus of claim 29 wherein the feed gas supply line further comprises a connection to an oxygen supply and an other supply.
 32. The apparatus of claim 35 wherein at least one of the other supply and the oxygen supply is a liquid.
 33. The apparatus of claim 35 wherein the other supply is a nitrogen supply.
 34. The apparatus of claim 29 wherein the product withdraw line removes a synthetic air product with an oxygen content of about 15% by volume to about 40% by volume.
 35. The apparatus of claim 29 wherein the product withdraw line removes a synthetic air product with an oxygen content of about 20% by volume to about 30% by volume.
 36. The apparatus of claim 29 wherein the product withdraw line removes a synthetic air product with an oxygen content of about 21% by volume. 